Spinal retractors have been developed for use in spinal surgery, such laminectomies, hemi-laminectomies, spinal fusions, repair of burst fractures, and the like, to provide surgeons with greater visibility and access to the surgical site. Spinal surgical areas benefiting from the use of retractors include, for example, the cervical, lumbosacral and the thoracolumbar regions. In order to reach the spinal area the surgeon typically must cut through several tissue layers, including the skin, fat, fascia and muscle, prior to reaching the vertebrae. The musculature in the lumbar area can be extremely resilient, requiring a great degree of force in order to retract the muscle; indeed, force on the order of 1200 pounds may be necessary to retract certain lumbosacral regions.
Retractor systems have been developed employing an assembly of blades, arms and a rack and pinion mechanism to position, spread and hold the tissue surrounding the spinal site. Typically, the blade portion is flat with straight sides, a set of teeth at the distal end for grabbing muscle, and is mounted at the proximal end to the arm by way of an aperture of some type that attaches transversely to the arm. In use, the blades are inserted into the surgical area and then attached to the arms of the rack and pinion mechanism. After positioning, the mechanism is cranked to spread the arms and retract the area, providing increased visibility and access to the surgical site.